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      <title>JVM类加载机制 - 交互式测验</title>
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      </style>
    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>JVM类加载机制 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
                    </div>
                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
                    </div>
                    <div id="result-container"></div>
                    <div id="hint-container" class="hint-container"></div>
                </div>
                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
                  <button id="hint-btn" class="nav-btn" style="background-color: #ffc107; color: #333; box-shadow: 0 4px 12px rgba(255,193,7,0.3);">提示</button>
                  <button id="next-btn" class="nav-btn">下一题</button>
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      </div>

      <script>
        const quizData = [
  {
    "question": "根据文档描述，在JVM类加载生命周期的“准备 (Preparation)”阶段，主要完成了什么工作？",
    "options": [
      "执行类的静态代码块和为静态变量赋予用户定义的初始值。",
      "为类的静态变量分配内存，并将其初始化为数据类型的默认值（如0, null, false等）。",
      "将常量池内的符号引用替换为直接引用（内存地址）。",
      "加载.class文件的二进制数据到内存中，并创建对应的Class对象。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "准备阶段的核心任务是为类的静态变量（即类变量）在方法区分配内存，并设置这些变量的初始值为其数据类型的默认值。例如，int类型的默认值是0，引用类型的默认值是null。而用户在代码中显式指定的初始值（如 `static int value = 123;` 中的 `123`）是在后续的“初始化 (Initialization)”阶段才会被赋予的。",
    "source": "文档中「类加载的生命周期」->「3. 准备（Preparation）」部分",
    "hint": "这个阶段只处理静态变量，并且赋予的是“零值”，而不是代码中指定的具体值。"
  },
  {
    "question": "文档中重点介绍了“双亲委派模型”，其最主要的设计目的是什么？",
    "options": [
      "提升类加载的性能，通过缓存机制避免重复加载。",
      "保证Java核心库的安全性和稳定性，防止核心API被用户代码意外或恶意篡改。",
      "实现模块化和插件化系统中的类隔离。",
      "允许开发者从网络、数据库等非标准来源加载类文件。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "双亲委派模型的核心思想是，一个类加载器在收到类加载请求时，会首先将请求委派给父加载器去完成，层层向上，直到顶层的启动类加载器。只有当父加载器无法完成加载时，子加载器才会尝试自己加载。这样做可以确保像 `java.lang.Object` 这样的核心类库始终由启动类加载器加载，从而防止了用户自定义的同名类对其进行覆盖，保障了Java平台的安全与稳定。",
    "source": "文档中「类加载器的工作原理」->「1. 双亲委派模型」部分",
    "hint": "思考一下，如果没有这个模型，用户自己写一个`java.lang.String`类会带来什么后果？"
  },
  {
    "question": "负责加载Java核心运行时库（如`rt.jar`中的`java.lang.*`）的类加载器是哪一个？",
    "options": [
      "应用类加载器 (Application ClassLoader)",
      "扩展类加载器 (Extension ClassLoader)",
      "启动类加载器 (Bootstrap ClassLoader)",
      "自定义类加载器 (Custom ClassLoader)"
    ],
    "correctAnswerIndex": 2,
    "explanation": "启动类加载器（Bootstrap ClassLoader）是JVM的一部分，处于类加载器层次结构的顶端。它负责加载Java最核心的类库，例如位于 `JAVA_HOME/lib` 目录下的 `rt.jar`。这个加载器是由原生代码（如C++）实现的，而不是Java语言本身。",
    "source": "文档中「类加载器的类型」->「1. 启动类加载器（Bootstrap ClassLoader）」部分",
    "hint": "哪一个类加载器是类加载器层次结构的“根”，并且没有父加载器？"
  },
  {
    "question": "根据文档中关于“类加载器隔离性”的示例，如果使用两个不同的自定义类加载器实例去加载同一个全限定名的类（例如`com.ts.MyClass`），那么比较这两个加载后得到的Class对象 (`class1 == class2`)，结果会是什么？",
    "options": [
      "结果为 `true`，因为它们的字节码完全相同。",
      "结果为 `false`，因为JVM中类的唯一性由其全限定名和加载它的类加载器共同决定。",
      "会抛出 `LinkageError`，因为同一个类被加载了两次。",
      "结果取决于这两个类加载器是否有相同的父加载器。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "在JVM中，一个类的唯一性是由它的全限定名和定义它的类加载器实例共同确定的。即使两个类来源于同一个`.class`文件，字节码完全一样，但只要加载它们的类加载器实例不同，那么这两个类就被JVM视为两个完全不同的类型。因此，`class1 == class2` 的比较结果必然是 `false`。这正是类加载器隔离性的体现，也是实现模块化、插件化等功能的基础。",
    "source": "文档中「类加载器的隔离性」->「4. 类加载器隔离性的示例」部分",
    "hint": "类的“身份证”不仅仅是它的名字，还包括它的“户口本”（即加载器）。"
  },
  {
    "question": "在实现一个遵循双亲委派模型的自定义类加载器时，官方推荐优先重写哪个方法来实现自定义的类加载逻辑？",
    "options": [
      "`loadClass(String name)`",
      "`defineClass(String name, ...)`",
      "`findClass(String name)`",
      "`getParent()`"
    ],
    "correctAnswerIndex": 2,
    "explanation": "实现自定义类加载器时，推荐的做法是继承 `java.lang.ClassLoader` 并重写 `findClass(String name)` 方法。`ClassLoader` 的 `loadClass` 方法内部已经实现了双亲委派的逻辑（检查缓存、委派父加载器）。只有在父加载器无法加载时，`loadClass` 方法才会调用 `findClass` 方法。因此，我们只需要在 `findClass` 中实现我们自己的类字节码获取和定义的逻辑即可，这样既能自定义加载行为，又不会破坏双亲委派模型。",
    "source": "文档中「自定义类加载器」->「1. 自定义类加载器的实现」部分",
    "hint": "我们应该在委派流程失败后才执行自定义逻辑，应该重写哪个方法来实现这一点？"
  },
  {
    "question": "参考文档中关于类初始化顺序的示例代码，当执行 `new Child()` 时，控制台输出的正确顺序是什么？",
    "options": [
      "Parent static block -> Child static block -> Parent instance block -> Parent constructor -> Child instance block -> Child constructor",
      "Parent static block -> Parent instance block -> Parent constructor -> Child static block -> Child instance block -> Child constructor",
      "Child static block -> Parent static block -> Child instance block -> Child constructor -> Parent instance block -> Parent constructor",
      "Parent static block -> Child static block -> Parent constructor -> Parent instance block -> Child constructor -> Child instance block"
    ],
    "correctAnswerIndex": 0,
    "explanation": "类的初始化顺序遵循严格的规则：1. 首先，初始化父类的静态部分（静态变量和静态代码块），按代码顺序。2. 接着，初始化子类的静态部分。3. 当创建实例时，先执行父类的实例初始化部分（实例变量和实例代码块），然后是父类的构造函数。4. 最后，执行子类的实例初始化部分，然后是子类的构造函数。因此，正确的顺序是先完成所有静态初始化（父类优先），再完成实例初始化（父类构造过程优先）。",
    "source": "文档中「类的初始化顺序」部分",
    "hint": "记住这个顺序：父类静态 -> 子类静态 -> 父类实例和构造 -> 子类实例和构造。"
  },
  {
    "question": "在类加载生命周期中，哪个阶段负责将常量池中的符号引用（如类名、方法名）替换为直接引用（如内存地址或偏移量）？",
    "options": [
      "验证 (Verification)",
      "加载 (Loading)",
      "准备 (Preparation)",
      "解析 (Resolution)"
    ],
    "correctAnswerIndex": 3,
    "explanation": "解析阶段的核心任务就是将常量池中的符号引用转换为直接引用。符号引用是一种文本形式的描述，与虚拟机内存布局无关。而直接引用则是指向目标的指针、相对偏移量或是一个能间接定位到目标的句柄，是与虚拟机内存布局相关的。这个转换过程为程序的实际运行做好了准备。",
    "source": "文档中「类加载的生命周期」->「4. 解析（Resolution）」部分",
    "hint": "哪个阶段是把“名字”变成“地址”的过程？"
  }
];
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        let currentQuestionIndex = 0;
        let score = 0;
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          optionsListEl.innerHTML = '';
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            const isCorrect = optionIndex === currentQuestion.correctAnswerIndex;

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            nextBtn.style.display = 'block';
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            nextBtn.disabled = false; // 最后一题时，下一题按钮不禁用，而是用于显示报告
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                hintBtn.disabled = true;
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            const resultBox = document.createElement('div');
            resultBox.className = `result-box ${isCorrect ? 'correct' : 'incorrect'}`;
            
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            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
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                // 高亮正确答案
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                    child.style.borderColor = '#c3e6cb';
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            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

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                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  